Silver ink containing silver complex compound has been used in various products such as conductive ink, electromagnetic wave shield, reflective film forming material, antimicrobial agent, etc. In particular, since the conductive ink has been recently spotlighted due to the regulation of lead use in an electric electronic component circuit and since it is advantageous when requiring a metal pattern or simply intending to form an electrode in new fields such as a low resistance metal wiring, a printed circuit board (PCB), a flexible printed circuit board (FPC), an antenna for a radio frequency identification (RFID) tag, an electromagenetic shield and plasma display panel (PDP), a thin film transistor liquid crystal display (TFT-LCD), an organic light emitting diode (OLED), a flexible display, and an organic thin film transistor (OTFT), etc. Also, as the electronic components tend toward compactness, the size of the metal particles used therefor becomes finer and finer.
The method for preparation of metal nanoparticles is divided into a physical method and a chemical method, wherein the physical method prepares it by physically grinding metal agglomerate and the chemical method is divided into a vapor reaction method and a liquid precipitation method.
The vapor reaction method is divided into an aerosol method preparing the metal nanoparticles by jetting a high pressure of gas, a pyrolysis method preparing powders through the pyrolysis using metal compound and gas reducer, and an evaporation/agglomerization method preparing powders by heating and evaporating evaporation materials. The liquid precipitation method is divided into a sol-gel method, a hydrothermal method, an ultrasonic decomposition method, a micro emulsion method, a liquid reduction method. In recent, the liquid reduction method using dispersant and reducer, which is easy in a shape control of powder and is highest in economy, has been the most widely used.
However, the methods preparing metal nanoparticles using the conventional liquid reduction method have disadvantages not suitable for mass production due to high preparation costs, complicated process, and low density of the metal thereof. Also, since safety is dropped or sintering temperature is high, it has various problems such that there is a limitation in being used in various kinds of substrates.
Japanese Laid-Open Patent Publication No. 2000-239713 discloses a method using ammonium polyacrylate polymer as dispersant and ascorbic acid as reducer, however, has a problem that precipitation of particles occurs.
U.S. Pat. No. 5,957,828 discloses a method for preparation of metal nanoparticles using reducer, while controlling temperature, however, has a problem in uniformity of nanoparticles.
Korean Laid-Open Patent Publication No. 2004-047100 discloses a method for preparation of nano silver powder by means of a wet reduction method, and more particularly a method for preparation of nano silver powder by means of a wet reduction method dissolving silver nitrate together with sodium dodecyl sulfate (SDS), sodium citrate (SC), polyacrylic acid (PAA), and polyvinyl pyrrolidone (PVP) to form intermediates, which are Ag—X based double compound, and injecting sodium hydroxide thereinto to generate Ag based composite oxide, and then injecting hydrazine or formaldehyde thereinto to reduce it, thereby preparing nano silver powder. However, the preparing method has a limitation in improving the preparation of various sized particles and the selectivity of particle size and has a problem in being used as ink composition, etc. due to large agglomerization of the prepared silver powder.
Korean Laid-Open Patent Publication No. 2005-040226 discloses a method for preparation of silver complex compound forming silver nitrate, which is a silver precursor, by dissolving silver in nitric acid, to dilute the prepared silver nitrate with water, adding ammonium hydroxide thereinto to form complex ions, injecting dispersant thereinto to prepare silver complex compound in a monodispersed sol state, controlling pH thereof in a base condition by means of sodium hydroxide and then reducing it by means of formaldehyde to dry it. However, it has a limitation in being used as ink composition, etc., since the control of the particle size, etc. is difficult and the silver particles are agglomerated to become an agglomerate state in a dry step so that it should be subject to a shattering process.
Therefore, it has been requested a method for preparation of silver complex compound that can minimize agglomerizaton of particles and prepare various shapes of silver complex compound, improve selectivity of the silver nanoparticle size, and be used for ink compositions to easily form a fine pattern or a uniform and densed thin film having high conductivity even when the it is fired during a short time to be suitable for being used as the ink compositions
Meanwhile, the present applicant has been filed a method for preparation of Ag complex [ammonium carbamate compound, ammonium carbonate compound or ammonium bicarbonate compound] by reacting silver compound with at least one or two mixtures selected from ammonium carbamate compound, ammonium carbonate compound or ammonium bicarbonate compound, as Korean Patent Application No. 2006-0011083. The application invention is useful as a method for preparation of silver complex compound. The present invention is related to the preparing method of the application invention.